Modular Gravitational Reference Sensor (modular GRS) was proposed by the Stanford Team in 2004. In a modular GRS, the laser beam from the remote the sensor does not illuminate the proof mass directly. The internal measurement from the housing to proof mass is separated from the external interferometry. A double‐sided grating further simplifies the structure and may better preserve the measurement precision. We review the recent progress in developing the modular GRS at Stanford. We are developing optical sensors with picometer resolution, capable of operating with a large gap for high precision readout. We have conducted an initial experiment incorporating RF heterodyne detection and thus lowered the optical power compared with direct detection. We have demonstrated sub‐nanoradian sensitivity of a grating angular sensor. We have successfully demonstrated fabrication of localized grating patterns on dielectric and gold surfaces. We have made critical progress in optical measurement of the mass center (MC) ...